Can't activate voicemail
I have a jailbreak iphone 2g. I can't activate voicemail. I've tried entering *5005*86*xxxx# to set the voicemail code. It gets set but when i tap the voicemail button, it prompts me to enter the mailbox number. I tried my carrier's voicemail number (1255 for grameenphone bangladesh) as well as my own phone number but it says the number is invalid. I have activated voicemail service from my carrier also. Even then it doesn't work.
Am i supposed to have voicemail APN in settings>general>network>cellular data network? because i have only one APN which is set to internet.
Any help is appreciated.....